1. Field of the Invention
The present invention relates to a electrical switching apparatus operating mechanism and, more specifically to an energy dissipating spring seat coupled to a spring operated ram within the operating mechanism.
2. Background Information
An electrical switching apparatus, typically, includes a housing, at least one bus assembly having a pair of contacts, a trip device, and an operating mechanism. The housing assembly is structured to insulate and enclose the other components. The at least one pair of contacts include a fixed contact and a movable contact and typically include multiple pairs of fixed and movable contacts. Each contact is coupled to, and in electrical communication with, a conductive bus that is further coupled to, and in electrical communication with, a line or a load. A trip device is structured to detect an over current condition and to actuate the operating mechanism. An operating mechanism is structured to both open the contacts, either manually or following actuation by the trip device, and close the contacts.
That is, the operating mechanism includes both a closing assembly and an opening assembly, which may have common elements, that are structured to move the movable contact between a first, open position, wherein the contacts are separated, and a second, closed position, wherein the contacts are coupled and in electrical communication. The operating mechanism includes a rotatable pole shaft that is coupled to the movable contact and structured to move each movable contact between the closed position and the open position. Elements of both the closing assembly and the opening assembly are coupled to the pole shaft so as to effect the closing and opening of the contacts.
Low and medium voltage electrical switching apparatus typically had a stored energy device, such as an opening spring, and at least one link coupled to the pole shaft. The at least one link, typically, included two links that acted cooperatively as a toggle assembly. When the contacts were open, the toggle assembly was in a first, collapsed configuration and, conversely, when the contacts were closed, the toggle assembly was, typically, in a second, toggle position or in a slightly over-toggle position. The spring biased the toggle assembly to the collapsed position. The spring and toggle assembly were maintained in the second, toggle position by the trip device.
The trip device included an over-current sensor, a latch assembly and may have included one or more additional links that were coupled to the toggle assembly. Alternately, the latch assembly was directly coupled to the toggle assembly. When an over-current situation occurred, the latch assembly was released allowing the opening spring to cause the toggle assembly to collapse. When the toggle assembly collapsed, the toggle assembly link coupled to the pole shaft caused the pole shaft to rotate and thereby move the movable contacts into the open position.
In a low and medium voltage electrical switching apparatus, the force required to close the contacts was, and is, typically greater than what a human may apply and, as such, the operating mechanism typically included a mechanical closing assembly to close the contacts. The closing assembly, typically, included at least one stored energy device, such as a spring, and/or a motor. Closing springs typically were about 2 inches in diameter and about 5 to 6 inches in length. These springs were structured to apply a force of abut 1000 pounds. A common configuration included a motor that compressed one or more springs in the closing assembly. That is, the closing springs were coupled to a cam roller that engaged a cam coupled to the motor. As the motor rotated the cam, the closing springs were compressed or charged. The toggle assembly also included a cam roller, typically at the toggle joint. The closing assembly further included one or more cams disposed on a common cam shaft with the closing spring cam. Alternatively, depending upon the configuration of the cam, both the closing spring cam roller and the toggle assembly cam roller could engage the same cam. When the closing springs were released, the closing spring cam roller applied force to the associated cam and caused the cam shaft to rotate. That is, the cam roller “operatively engaged” the cam. Rotation of the cam shaft would also cause the cam associated with the toggle assembly cam roller to rotate. As the cam associated with the toggle assembly cam roller rotated, the cam caused the toggle assembly cam roller, and therefore the toggle assembly, to be moved into selected positions and/or configurations. More specifically, the toggle assembly was moved so as to rotate the pole shaft into a position wherein the contacts were closed. Thus, the stored energy from the closing springs was transferred via the cams, cam shaft, toggle assembly, and pole shaft to the contacts.
For example, during a closing procedure the toggle assembly would initially be collapsed and, therefore, the contacts were open. When the closing springs were released, the rotation of the cam associated with the toggle assembly cam roller would cause the toggle assembly to move back into the second, toggle position, thereby closing the contacts. This motion would also charge the opening springs. Simultaneously, or near simultaneously, the trip device latch would be reset thereby holding the toggle assembly in the second, toggle position. After the contacts were closed, it was common to recharge the closing spring so that, following an over current trip, the contacts could be rapidly closed again. That is, if the closing springs were charged, the contacts could be closed almost immediately without having to wait to charge the closing springs.
While this configuration is effective, there are a substantial number of components required, each of which requires space to operate within and each of which are subject to wear and tear. Further, certain components are exposed to considerable force, which enhances wear and tear, during operations wherein that particular component is not in use. Accordingly, one improvement to this configuration is to include a ram assembly structured to act directly on the toggle assembly, as disclosed in the related application set forth above. That is, rather than utilizing a closing spring coupled to a roller to operatively engage a cam and having the toggle assembly with a roller coupled to another cam, the Spring Driven Ram For Closing A Electrical switching apparatus utilizes a spring driven ram that engages the toggle assembly.
The ram assembly includes a ram body that travels on at least one, and preferably two, guide pins between a first, retracted position and a second, extended position. When the ram body is in the first, retracted position, the ram assembly springs are compressed. The toggle joint, when collapsed, is disposed in the ram body path of travel. Thus, when the ram assembly is released, the ram body moves over a path of travel to the second, extended position. While moving, the ram body engages the toggle joint and moves the toggle assembly into its over-toggle configuration.
The ram body path of travel is defined by a guide assembly having, preferably, two guide pins. The guide pins are maintained in a spaced, generally parallel relationship by a base plate at one end and a stop plate at the other end. The ram assembly springs are disposed between the base plate and the ram body and are structured to bias the ram body toward the stop plate. When the springs are charged and the ram assembly is released, the ram body moves over the guide pins and impacts the stop plate.
While the ram assembly requires few components, reduces the wear and tear on those components and may fit into a reduced space, the ram assembly, and more specifically the spring(s) of the ram assembly, cause an increase in stress on the supporting structure, i.e. the housing assembly or a frame assembly. That is, when the ram body impacts the stop plate, there is stress on the stop plate as well as stress on the base plate. There is, therefore, a need for a device structured to dissipate the energy of the ram assembly springs following a release of the ram assembly. There is a further need for a device structured to dissipate the energy of the ram assembly springs that may be incorporated into a reduced space.